How the North American Air Defense Identification Zone Works

One issue at the center of the row over China’s new Air Defense Identification Zone is how China plans to enforce the regulations it has announced: will it simply escort planes who refuse to comply, or try to repel them or force them to land?

China’s rules, which are listed here, say its military will take “defensive emergency measures” against aircraft that don’t comply with the zone’s rules. But they don’t specify those measures.

Such zones aren’t governed by international treaties or organizations and are usually established unilaterally by individual governments, so rules vary between each one and can be adjusted and enforced at will.

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But many adhere roughly to the rules in the North American ADIZ, which covers the U.S. and Canada. Those rules are listed here.

The rules technically require most foreign aircraft to file a flight plan with U.S. authorities before departure and to report their position to the relevant U.S. aeronautical facility “at least one hour prior to ADIZ penetration.”

They also provide details on how U.S. military aircraft identify, monitor and intercept planes within the ADIZ. Here’s a diagram:

Federal Aviation Administration

Here are some of the rules for interceptions:

1. Approach Phase.
As standard procedure, intercepted aircraft are approached from behind. Typically, interceptor aircraft will be employed in pairs, however, it is not uncommon for a single aircraft to perform the intercept operation. Safe separation between interceptors and intercepted aircraft is the responsibility of the intercepting aircraft and will be maintained at all times.

2. Identification Phase.
Interceptor aircraft will initiate a controlled closure toward the aircraft of interest, holding at a distance no closer than deemed necessary to establish positive identification and to gather the necessary information. The interceptor may also fly past the intercepted aircraft while gathering data at a distance considered safe based on aircraft performance characteristics.

3. Post Intercept Phase.
An interceptor may attempt to establish communications via standard ICAO signals. In time-critical situations where the interceptor is seeking an immediate response from the intercepted aircraft or if the intercepted aircraft remains non-compliant to instruction, the interceptor pilot may initiate a divert maneuver. In this maneuver, the interceptor flies across the intercepted aircraft’s flight path (minimum 500 feet separation and commencing from slightly below the intercepted aircraft altitude) in the general direction the intercepted aircraft is expected to turn. The interceptor will rock its wings (daytime) or flash external lights/select afterburners (night) while crossing the intercepted aircraft’s flight path. The interceptor will roll out in the direction the intercepted aircraft is expected to turn before returning to verify the aircraft of interest is complying. The intercepted aircraft is expected to execute an immediate turn to the direction of the intercepting aircraft. If the aircraft of interest does not comply, the interceptor may conduct a second climbing turn across the intercepted aircraft’s flight path (minimum 500 feet separation and commencing from slightly below the intercepted aircraft altitude) while expending flares as a warning signal to the intercepted aircraft to comply immediately and to turn in the direction indicated and to leave the area. The interceptor is responsible to maintain safe separation during these and all intercept maneuvers. Flight safety is paramount.

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